Projection type video display

Abstract

A doughnut-shaped dust-proof plate is externally fitted in the body of the projection lens. The dust-proof plate comprises a first member which is flexible like rubber and a second member made of plastic which is uneasy to deform. The second member is made lower in a vertical direction (lengthwise) than the first member, thereby making it possible to allow deformation at an upper end and a lower end of the first member. On the other hand, the second member is made long in a horizontal direction (crosswise). A longitudinal portion of the second member is set to have such a length that it can come into contact with a lower wall of the frame of the liquid crystal projector even if the projection lens is positioned at the uppermost position and can come into contact with an upper wall of the frame even if the projection lens is positioned at the lowermost position in a state where the dust-proof plate is obliquely turned. Therefore, the dust-proof plate is prevented from being turned at an angle of 90 degrees.

Description

BACKGROUND OF THE INVENTION Field of the Invention [0001] The present invention relates to a projection type video display comprising a lens shift mechanism. [0002] Examples of a projection type video display include a liquid crystal projector. A known liquid crystal projector comprises a lens shift mechanism for moving a projected video up and down with its main body kept immovable and preventing the projected video from having a trapezoidal shape (JP-A-09-138377). SUMMARY OF THE INVENTION [0003] In a lens shift mechanism, a relatively large lens shift width can be ensured in a vertical direction (lengthwise) or a horizontal direction (crosswise). For this purpose, a large clearance must be ensured between a projection lens and an aperture of a front cover in a liquid crystal projector in correspondence with the lens shift width. However, the large clearance between the projection lens and the aperture of the front cover not only loses design but also allows dust to easily enter a ...

AI Technical Summary

Benefits of technology

[0003] In a lens shift mechanism, a relatively large lens shift width can be ensured in a vertical direction (lengthwise) or a horizontal direction (crosswise). For this purpose, a large clearance must be ensured between a projection lens and an aperture of a front cover in a liquid crystal projector in correspondence with the lens shift width. However, the large clearance between the projection lens and the aperture of the front cover not only loses design but also allows dust to easily enter a frame of the projector.

[0004] In view of the foregoing circumstances, an object of the present invention is to provide a projection type video display capable of further preventing dust from entering its frame even when a large clearance is ensured between the projection lens and an aperture of a front cover.

[0006] In the above-mentioned configuration, the plate member is provided to close the clearance between the aperture and the projection lens on the reverse surface of the front cover. Even when a large clearance is ensured between the projection lens and the aperture, therefore, dust can be prevented from entering a frame of the projection type video display.

[0007] The plate member may be constructed by affixing a first member having flexibility and a second member which is uneasy to deform. Consequently, the durability can be significantly improved, as compared with that in a case where the plate member is composed of only the first member having flexibility.

[0009] In the projection type video display having such a configuration, the plate member may be externally fitted in the body of the projection lens, and the plate member may be connected to a movable member on which the projection lens is mounted in the lens shift mechanism. In such a configuration, the plate member can be prevented from being undesirably turned and moved.

[0010] Alternatively, in the projection type video display having such a configuration, the plate member may be externally fitted in the body of the projection lens, and there may be further provided a restraining member for restraining the movement of the plate member by touching the plate member. In such a configuration, the plate member is simply externally fitted in the body of the projection lens. As a result, the assembling work is significantly easy.

Problems solved by technology

However, the large clearance between the projection lens and the aperture of the front cover not only loses design but also allows dust to easily enter a frame of the projector.

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